The present invention relates generally to oil seals, and more particularly, to a composite seal assembly adapted for specialized applications. According to the present invention, a novel form of seal is provided which makes possible the elimination of cumbersome, relatively unreliable former designs for certain special applications. In particular, the seal design of the present invention makes installation of rear crankshaft seals much easier and more reliable.
While the present invention has other applications, the primary application, that of a rear crankshaft seal, has historically presented a number of serious problems. In some engine designs, the portion of the crankshaft over which the lip of the oil seal is required to extend is a reduced diameter portion of the crankshaft. Accordingly, it was sometimes customary to wrap a rope-type packing around such reduced diameter crankshaft end portion. In other applications, the seal has been manufactured in two mating halves, and installation required not only positioning one of the seal halves in a narrow recess lying within a part of the engine block above the crankshaft bearing journal, but also required precise mating of the lower half of the seal with the upper half so that there was no leakage along the surfaces at which the two half seals met in end-to-end relation. In addition, it was often difficult to align the seal so that the seal lip would lie in a single plane to provide an effective seal. In many cases, these problems were aggravated because the material used to form the seal lip was one which lacked mechanical strength and toughness; silicone rubbers for example, were often used in this application. This made a good seal between seal halves but the material lacked toughness and could be damaged during installation.
Another problem common not only to rear crankshaft applications but to seal installations generally, is the matter of quality control under conditions where part of the seal assembly is made by one manufacturer and the other part or parts are made by one or more other manufacturers. This situation may be aggravated where installation is done by assembly line personnel who represent a still further element in the assembly process. Modern quality assurance concepts call for placing the responsibility for an assembled element with a single person or source, where possible. Accordingly, any arrangement wherein different elements of an assembled part are supplied from different sources or are assembled by different personnel create situations wherein it is difficult to maintain quality, and to pinpoint responsibility in the event of failure.
According to the present invention, a seal assembly can be provided which eliminates the need to machine a counterbore in the end of the engine block. This operation may thus be eliminated.
The present invention provides a composite seal which insures easy alignment and ready fastening to a flat face portion of an engine block or related part. Moreover, the invention provides a retainer element which may be made from a synthetic plastic material at low cost, to close tolerances, and which is susceptible of receiving and precisely locating a retainer insert which in turn carries an elastomeric seal body. The invention is particularly compatible with modern manufacturing techniques, and has a number of incidental advantages as well.
In its preferred form, the invention provides a crankshaft seal assembly which includes a molded plastic retainer element having fastener inserts received therein and which further includes a shoulder surface arrangement for receiving and positioning a retainer insert which may be affixed by ultrasonic welding or the like in fluid tight relationship to the retainer.
The insert carries a fluoroelastomer or similar tough, high temperature resistant seal unit which directly engages a surface on a portion of the crankshaft or a similar surface to be sealed. Still further, according to the invention, the retainer itself includes, in addition to a mounting portion, a portion encircling the rear crankshaft extension, an outer surface adapted to be engaged in fluid-tight, static relation by the engine oil pan. This further simplifies and improves the reliability of installation. The present invention provides these and a number of other advantages, including the advantages of enabling an elastomeric seal unit body of small volume to be made available for this installation.
In view of the failure of the prior art to provide a fully satisfactory, economical and reliable rear crankshaft seal, it is an object of the present invention to provide an improved composite seal assembly.
Another object of the invention is to provide a composite seal assembly which includes three separate elements which are combined by the manufacturer into a unitary, easy-to-install assembly.
A still further object of the invention is to provide a composite seal assembly which includes a retainer element molded from a plastic material, a retainer insert unit which is affixed in fluid tight relation to a center opening in the retainer element, and an elastomeric seal unit which is bonded to one or more selected surfaces of the retainer insert and which engages a movable machine part extending through the center seal opening.
Yet another object of the invention is to provide a composite seal element whose components may be manufactured with minimum tooling expense and at low cost using high volume molding techniques.
A further object of the invention is to provide a multi-part seal whose elements may be assembled under the control of a single manufacturer.
A still further object of the invention is to provide a composite seal assembly which is readily aligned and positioned relative to a fixed machine member, with a portion of the assembly encircling a relatively movable machine member and which composite seal may be reliably installed without damage in a predetermined position of use.
Another object of the invention is to provide a seal which readily mates in fluid tight relation with other parts, including a movable machine member and a pair of stationary machine members.
A further object of the invention is to provide a seal assembly wherein one of the elements may be affixed in a precise relation to another by ultrasonic welding techniques.
A still further object of the invention is to provide a composite seal assembly wherein two of the components are made from different thermoplastic, injection molded materials, one of which is readily insert molded with and bonded to an elastomeric seal unit.
Yet another object of the invention is to provide a method of manufacturing an improved seal to provide a sealed mechanism which includes at least one stationary part and at least one movable machine member and in which the fluid is confined to the interior of the sealed mechanism by a composite seal unit which includes a pair of relatively rigid plastic elements and a bonded elastomeric seal unit.
Another object of the invention is to provide a multi-element seal unit which is resistant to damage during installation, resistant to fatigue in use, and which will assure proper alignment and positioning relative to both fixed and movable elements.
A still further object of the invention is to provide a seal assembly which eliminates the need for performing certain finishing operations on the remainder of the seal unit.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a composite seal unit which includes a retainer element adapted to be affixed to a machine member in fluid tight relation, with the retainer element including a center opening having means for receiving a retainer insert, a retainer insert positioned within said opening both radially and axially in a desired position of use, with the insert having an elastomeric seal body bonded to a portion thereof in fluid tight relation and with the seal body including frusto-conical surfaces meeting each other to define a seal band along a generally circular locus to provide a seal band of intended contact with a relatively movable machine element extending outwardly from the first unit. The invention is also achieved in practice by providing such an assembly having the retainer and the retainer insert made from synthetic plastic materials, and by providing methods and apparatus for making such a seal assembly.
The exact manner in which the foregoing and other objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, in which like reference numbers indicate corresponding parts throughout.